Gameboid - does NOT play GB/C games, only GBA. Still great tho.
SNesoid - controls are quite awkward on the device... not feasible for all.

moving along:

NESoid - it has one major advantage over any other NES emulator you've ever used: DUCK HUNT. Use that touchscreen as a light gun! Kinda makes you wish better light gun games were made... only a dozen or so came out, and that includes the duds.

Gensoid - same as SNesoid, sadly. Otherwise I'd love to have Sonic 3 & Knuckles on my phone. Easily my favorite game of all time.

best game I have played on my droid is definitely bonzai blast. I had played zuma deluxe on my computer and its similar game if not better. I haven't seen it on the market for a while, but it was there last month for free, not sure where it went.

jewel is great too.

the emulators like snesroid are wonderful, I will agree 100% about the light gun games like duck hunt, though some of them don't work with snesroid at least, it is missing buttons or something (it only has the fire button). If you can get it to work, it works well, try battleclash for snes. Along the same vein I have tried playing fzero with the accelerometer sensors to steer but the control is way too sensitive. My conclusion is the one thing holding the emulator games back is the controls.

Armored Strike - Like Worms. Choose weapon, adjust shot angle & velocity, Hope it hits someone, Next turn adjust. It's a good system that's been working for a long time.

Cestos - Still play this one a ton. Billiards physics in a multi-player online combat game. I like the Sumo stage the best.

Parallel Kingdom - A MMORPG like world of warcraft. Is GPS based and played over the top of google maps, though there are ways to explore without actually going somewhere, so you can still play this if you're a shut-in. I actually had to stop playing because I was spending way too much time on it and my girl didn't appreciate it.

Space Physics - Super awesome puzzle game. You're given a stage and you have to move a ball to touch a goal. You draw lines and objects as well as a few specialized tools like a piviot point and car to direct your ball there.

What The Doodle - Like Pictionary/Win Loose Or Draw. Played online.

The Plateau - Puzzle Game. Simple concept yet can get very complicated. Given a series of nodes connected to each other by lines. Move the nodes to untangle the lines so none are overlapping. Bonuses for tapping nodes that light up. Great game. I've been playing this one the most.